Final HG Torque numbers?

[hippiekiller]

I had a little incident which resulted in me applying the final 90* hot torque at around 600km...Besides the fact that I'm pretty sure that I cooked the head, I would like to just check the bolts with a torque wrench cold to see if I am in any sort of ballpark....Would anybody have some rough idea of what I should be seeing as far as ft.lbs?

[theman53]

Mark the miser or something like that has them. IIRC it was around 105ft lbs, but DO NOT quote me on that.

[Mark(The Miser)UK]

Hi,
This is what I have personally experienced. This is for M12 stretch bolts

I use a Snap-On dial gauge torque wrench. IIRC it's 2% or better.

Initial angular torquing peaks at approximately 115 to 125lbft.

The final torquing only reaches 95 to 105lbft...
I have done this warm. I believe this is optional but I like the idea that the gasket is slightly more pliable when warm, and likely to fill any divots. I might be wrong on that, but it's just how I do it because I have justified it to myself.  .

A little more on 'my' procedure. I could  be wrong, so it's just for reading, but I've not failed yet...

With the 90 degree torques, I actually only torque until value levels off. This may result in only 45 deg.
I  split the 180 deg turn in two, for a 'more even' clamping [or so I tell myself]

To avoid that nasty bind and cracking sound  that I'm sure we've all experienced as we torque some of the head bolts up, I still use the old method of slackening each bolt in turn [release water cap if done with any real warmth remaining]

The final torque gives a nice smooth rise to the afore mentioned figures. Slackening actually reveals just how slack some of the bolts have become, yet [hopefully] not allowed any leaks. 

Remember slackening a bolt that has not been set for years, will never repeat the torquing up values so you will only see about half the values. [or less occasionally ]

By not using up all of the angular torquing on the first use, I personally reuse the bolts once more. I don't advocate doing that, but by having the angular stretch in reserve, can also be useful for shutting  off that slight gasket leak that may develop early on.

[hippiekiller]

Very good info, thank you....Hopefully I wont have to do it a second time.... Mine all measured out at around 110-115 this morning, so if I keep blowing coolant hoses I'll have to take the head off again....

[Mark(The Miser)UK]

Very good info, thank you....Hopefully I wont have to do it a second time.... Mine all measured out at around 110-115 this morning, so if I keep blowing coolant hoses I'll have to take the head off again....

In my limited research into gasket leaks, if you can catch a minor leak early enough, you may be able to squeeze it shut again, but if it's been going on unnoticed for a while, then it gets harder to close the tunnel down. Maybe these clogging agents might work, but hard to get pressure up enough from the coolant side. I suppose that a small enough leak could clog up with carbon.

Maybe a trick would be to run an engine relatively 'rich', such that soot fills it up

[hippiekiller]

       Thats my problem, I still have a tiny leak somewhere...while I look for a new head, Would it be considered foolhardy at this point to try and torque them all to say, 115? I  am imagining that the block will strip before the bolt breaks??
      I am only getting the tiniest of bubbles in the resevoir, and am hoping its not one of the small cracks between the valves (didnt have the head press tested) but the coolant system holds pressure....

[R.O.R-2.0]

       Thats my problem, I still have a tiny leak somewhere...while I look for a new head, Would it be considered foolhardy at this point to try and torque them all to say, 115? I  am imagining that the block will strip before the bolt breaks??
      I am only getting the tiniest of bubbles in the resevoir, and am hoping its not one of the small cracks between the valves (didnt have the head press tested) but the coolant system holds pressure....

the bolt will break before the block strips.. as long as its a 12mm block.

11mm block may be a different story..

[hippiekiller]

Would it be better for me to retorque it warm (operating temp) again to try to squeeze this leak shut?  

And  Mark, are you saying that it can be allright to slacken TTY bolts and then re-torque?

Would it be worth it for me to just buy a new set of headbolts and try a complete new clamp down with the existing (fairly new but already formed) gasket?

[Mark(The Miser)UK]

Would it be better for me to retorque it warm (operating temp) again to try to squeeze this leak shut? 

And  Mark, are you saying that it can be allright to slacken TTY bolts and then re-torque?

I would do it hot, to gain from any softening effect, but once hot release water pressure.
I personally do the final retorque, and any subsequent torquing this way.
I also always slacken one at a time.
I then torque until value levels off. I make sure I'm positioned over the gauge...
 Likely as not you won't reach 115lbft

[Luckypabst]

...Besides the fact that I'm pretty sure that I cooked the head

Would it be worth it for me to just buy a new set of headbolts and try a complete new clamp down with the existing (fairly new but already formed) gasket?

I think your time would be best spent removing the head and checking for excessive warp, repairing as necessary, then installing a new headgasket with new head bolts, following the factory torque procedure.

There's plenty of science behind the angle torque procedure and there's no need for anyone to attempt to out-engineer the OEM team of engineers.

Of course there's little harm in trying to salvage what you have, except for possibly over torquing the bolts, which could cause the bolt to fail, or unknowingly release tension as you pass the ultimate tensile strength, leading to the issue of uneven tension across the gasket interface from uneven/excessive bolt torque.

Chris

[hippiekiller]

I have pretty much resigned myself to taking the head off again and having it milled, just cant do it right now.....

[Mark(The Miser)UK]

I have pretty much resigned myself to taking the head off again and having it milled, just cant do it right now.....

Then try my method. You have nothing to lose. Heck you could even epoxy the gasket on the block side. I think OEM engineers from this period were at the leading edge of those having their hands tied behind their back, for the sake of company profit above all else.

I've actually used brand new stretch bolts [yep even I buy them, although half as often as some  ]
At the same time as putting them through their 90 degree stretches, I've noted the peak and levelling of the forces occuring have noticed that there is a range of clamping force applied by this official method.
I can safely say that it is at least 20lbft.

As far as my tired brain can guesstimate that is 1000's of lb force variation.
So much for improving things... You still need a torque gauge to do the first few stages

I assume the variation is hiding in amongst  metallurgy of the bolt, or composition of gasket, or variation in lubrication.

[Luckypabst]

Then try my method. You have nothing to lose. Heck you could even epoxy the gasket on the block side.

I agree with this, Mark... but angle torquing is a far more accurate & repeatable method than using a torque wrench, that isn't influenced by inconsistencies in lubrication, thread condition, torque wrench accuracy or even the mechanic's procedure.

Chris

[Mark(The Miser)UK]

Then try my method. You have nothing to lose. Heck you could even epoxy the gasket on the block side.

I agree with this, Mark... but angle torquing is a far more accurate & repeatable method than using a torque wrench, that isn't influenced by inconsistencies in lubrication, thread condition, torque wrench accuracy or even the mechanic's procedure.

Chris
I'd like to agree with you. After all 90 degrees can be pretty accurately done, and 180, more so.
However, with the actual torque reading varying between 2 bolts say 110lb, and 125lb.  Is this more 'matched' than using a gauge and settling for 105lbft for both?
Variation in the stretched torque tells me that maybe one bolt is further into the plastic range than the other. Further entry into the plastic range, to me seems pointless, but maybe that is part of the procedure to ensure that you are in it.
How far into the plastic range do you need to be for 'satisfactory' clamping?

Permanant deformation of the bolt is part way into breaking it...How far? "Please use only once" far, it would seem.

If what is said by OEM engineers is best for the customer, then why does the original VAG instruction manual for the 1.5/1.6 diesel engine say " Distortion limit for head 0.1mm. Do not rework"

In the same September 1982 workshop manual, there is an iinserted bulletin update in 1983 November, stating that...well you all can read it!Click twice for big pic...


Anyway back to the discussion. I'd never suggest anything that I hadn't actually done or intend to in the future. I've never lost a bolt using my method,or had a gasket leak beyond the 600 mile retorque after all I'm actually stressing the bolt less than standard, leaving room for more adjustment later...Sometimes it's just not convenient to order new parts!